1. Field of the Invention
The present invention relates to a composite valved graft, and more particularly, to an artificial valved conduit that is a composite valved graft comprising double sewing cuffs, which can be easily used in aortic root replacement.
2. Description of the Conventional Art
In general, aortic root replacement is a surgery in which, when aortic valve regurgitation is accompanied in a patient suffering from ascending aortic aneurysm that intrudes the patient's aortic root, the lesion part is excised, and an artificial valved conduit that is a composite valved graft is used.
Each of the existing composite valved grafts used in the aortic root replacement is generally configured with a sewing cuff, an artificial valve, and a conduit part connected thereto. In replacement using such a composite valved graft, when an anastomosis is performed, a medical specialist closely sutures a sewing cuff of the composite valved graft and a cut part of a blood vessel relying upon manual work. However, problems frequently arise in the anastomosis stage.
The aortic root replacement, because of its characteristics, involves operating on a wide area. In the aortic root replacement, after the aortic root is excised, an artificial valve and artificial blood vessels are anastomosed at a deep part of the heart, and entrance parts of the left and right coronary arteries are anastomosed. As such, the number of parts involved in anastomosis is greater than that in heart surgery, and hence lengthening the operating time of the aortic root replacement.
Aortic root replacement is not only complicated but, also a type of surgery in which it is difficult to detect the loss of blood after anastomosis. In relation to the aortic root replacement, several methods for reducing the loss of blood have been studied and proposed, but the frequency of bleeding is reported as 5 to 13% (Long-Term Mortality and Morbidity after Button Bentall Operation, J Card Surg, 2013, Vol.28; pp.280-284).
If blood loss occurs where anastomosis has been performed, several problems occur. In this case, such problems include a need for a reoperation, extension of extracorporeal circulation time, and heart ischemia time, transfusion of a large amount of blood, and the like. This has a negative impact on the patient financially as well as on the patient's health. Particularly, when bleeding occurs at is the rear of a proximal conduit, it may be difficult to perform re-anastomosis.
As a method for preventing the loss of blood, a method has been conceived of surrounding a transplanted conduit with the patient's aortic wall, a method of connecting the aortic wall, and the right atrium, a method of anastomosing the aortic wall to the artery conduit, performing reinforcement anastomosis surgery using self-pericardium, and the like. However, a large number of disadvantages have been reported regarding these methods.
Conventionally, sewing cuffs were devised to overcome disadvantages in the anastomosis surgery and to minimize side effects. As an example, U.S. Pat. No. 6,351,573 discloses various types of sewing cuffs surrounding the outer circumference of a valve. However, the disclosed sewing cuff is made of a semi-rigid material so that suturing is performed only when a suture fiber passes through holes provided in the sewing cuff. Therefore, there is an inconvenience in that the suture fiber is to pass through each hole for the purpose of airtight suturing. The disclosed sewing cuff additionally provides an adherence band which can be connected to the circumference of a valve, so that it is possible to more easily prevent the loss of blood. However, the sewing cuff varies widely in applicability according to surgical parts and situations. Since the shape of the sewing cuff is complicated, the sewing cuff can be easily used after a user is good at the use of the sewing cuff, and the efficiency of the sewing cuff may deteriorate with time. In addition, there is an inconvenience in that effects of a technique disclosed according to each surgical situation can be obtained only when the user is fully aware of usage according to the kind of sewing cuff, and it is very difficult to apply the sewing cuff to actual clinical practice.
As another example, in PCT Patent Publication No. WO 2012-162522, the sewing cuff comprises one or more sewing cuffs on the outer circumference of an artificial valve in order to perform a more efficient and convenient anastomosis surgery between the valve and an annulus. A first sewing cuff is positioned on the outer circumference of the valve and has a height that is not less than 50% of the height of the valve in a closed state. A second sewing cuff narrower than the first sewing cuff is positioned on the outer circumference of the first sewing cuff. The second sewing cuff having a crown shape or a shape with upper and lower parts alternately placed in the vertical direction is positioned on the first sewing cuff. Thus, it is possible to prevent the deformation of a blood vessel surface that is caused when human tissue is aligned with the sewing cuff during the anastomosis surgery. Accordingly, the sewing cuff can be more easily used in suturing. That is, since the aortic annulus in a human body is not formed in a horizontal shape but anatomically formed in a fan type crown shape, the sewing cuff of the artificial valve, disclosed in PCT Patent Publication No. WO 2012-162522, is manufactured in the same shape suitable for the aortic annulus, so that it can be expected that the difficulty in nadir suture of the annulus will be dissolved.
However, the substantially efficient application range of the sewing cuff is limited to the annular nadir of tissue valve root by the special shape and position of the second sewing cuff. As a result, due to the special shape of the second sewing cuff, there is still an inconvenience in that the human tissue imust be aligned with the sewing cuff. Meanwhile, aortic valve regurgitation is generally accompanied in artificial blood vessel replacement comprising a valve. In this case, although the crown-shaped sewing cuff has a shape different from those of the existing sewing cuffs, when it is substantially applied, a big difference in view of efficiency for suppressing the aortic valve regurgitation cannot be expected just as it is with the traditional sewing cuffs because double suturing is not performed. Furthermore, since the annulus is expanded during an actual surgery, the necessity of having to use a crown-shaped sewing cufflessens.
As described above, there have been proposed sewing cuffs on the outer circumferences of various types of artificial valves in order to prevent the loss of blood after an anastomosis surgery is performed. However, applicable situations are limited due to the complicated or special shape of the sewing cuff, and there is an inconvenience in that a user must familiarize oneself with the usage of the sewing cuff beforehand. Although the loss of blood can be reduced by using the sewing cuff, because it may take a longer time to use the sewing cuff the efficiency is lessened by comparison. The conventional composite valved grafts and the sewing cuffs included therein, have limits when it comes to solving these problems.